Breast cancer can be understood as a series of stressors, including physical symptoms, treatment side effects, fears about disease progression, and disruption of social and vocational roles. Stress can be further exacerbated by social isolation and maladaptive coping, which may in turn adversely affect the endocrine system, and potentially the rate of disease progression. Conversely, enhanced psychosocial support via group therapy or other means may improve medical outcome by buffering the consequence of such stress and thereby ameliorating endocrine function. Previous research in this laboratory with metastatic breast cancer patients has demonstrated an association between diurnal cortisol rhythms and survival, revealing flatter slopes (i.e, loss of normal diurnal variation to be associated with shorter survival. This is of particular importance because glucocorticoids have been shown to facilitate tumor growth. This program of research is designed to examine the relationships among stress, dysfunction of the hypothalamic-pituitary-adrenal axis [HPA], and breast cancer progression. A sample of 100 women with hypothalamic- pituitary-adrenal axis [HPA], and breast cancer progression. A sample of 100 women with metastatic breast cancer will be recruited for intensive evaluation of their stress response. Salivary cortisol samples will be taken to determine the pattern of diurnal variation in cortisol and to examine its relationship to stress and survival time. Regulation of the stress response system will be studied utilizing low-dose activation of cortisol will be evaluated using the Trier Social Stress Task. This systematic assessment of stimulation and suppression of the cortisol stress response and its relationship to breast cancer progression will thoroughly examine the hypothesis that endocrine dysfunction may mediated the relationship between stress and breast cancer progression.